Oil sands deposits are found in over seventy countries throughout the world. However, a substantial portion of these deposits are located in the Alberta oil sands. In fact, Alberta's oil sands deposits contain the largest known reserve of oil in the world. The vast quantities of oil in these deposits creates a tremendous incentive to develop and improve upon techniques and systems for recovering them.
Oil sands are a geological formation, which are also known as tar sands or bituminous sands. Oil sands deposits are primarily composed of solids (generally mineral components such as clay, silt and sand) plus bitumen and water. The bitumen content typically constitutes up to about 21 wt. % of the bitumen-bearing formation material, with the remainder of the formation material composed of about 70 to 85 wt. % solids and about 4 to 10 wt. % water. The solids content typically includes clay and silt ranging from about 5 to 50 wt. %. Technically speaking, the bitumen is neither oil nor tar, but a semisolid form of oil which will not flow toward producing wells under normal conditions, making it difficult and expensive to produce.
Oil sand deposits are mined using strip mining techniques or persuaded to flow into producing wells by techniques such as steam assisted gravity drainage (SAGD) or cyclic steam stimulation (CSS) which reduce the bitumen's viscosity with steam, solvents or a combination of steam and solvents.
In order to produce an appropriate quality of bitumen-based product for use by a refinery, the hydrocarbons in the bitumen-bearing formation material removed from oil sands deposits need to be concentrated. Concentrating the hydrocarbon content of a bitumen-bearing material (also known as bitumen recovery) is typically carried out through primary and secondary treatment processes that are well known in the art.
In conventional primary treatment facilities, the bitumen-bearing formation material is processed to produce a bitumen-enriched froth stream, which typically has a bitumen content of about 50 to 60 wt. %, a solids content of about 10 to 15 wt. % and a water content of about 30 to 40 wt. %. The bitumen-enriched froth stream that is produced through primary treatment is typically transported to a secondary treatment facility to increase its hydrocarbon concentration further in order to make it suitable for processing by an upgrader or specialized refinery facility. In order to make use of the bitumen-enriched froth stream in an upgrader or refinery, secondary treatment facilities process the stream in order to produce a hydrocarbon-rich product having a hydrocarbon concentration typically in the range of at least about 90% to 97% wt. % or more. Various techniques may be used to enhance the hydrocarbon concentration of the bitumen-enriched froth stream produced by primary treatment processes, examples of which can be found in Canadian Patent Nos. 873,854, 882,667 and 2,400,258.
Although various treatment processes exist to produce a bitumen-enriched product suitable for use by an upgrader or refinery, there continues to be a need for further treatment processes and systems that offer enhancements or alternatives to the manner in which a bitumen-enriched froth stream from primary treatment is processed.